Devisible pyrotechnic device

ABSTRACT

An illuminating body which is attachable to a parachute is divided into a number of partial flares which slant outward from the axis of the body at given angles by virtue of the fact that an elongated body of pyrotechnic material is divided into a number of axial sections which fan out from a common connection at one end.

Elite ttes atet' 1 Simmons Feb. 12, 1974 [54] DEVISHBLE PYROTECHNIC DEVCE FOREIGN PATENTS OR APPLICATIONS [75] Inventor: gi 3"? Simmons, 650,094 9/1928 France 102/352 ar s oga, we en [73] AssIgnee: Aktlebolaget Bofors, Bofors, Sweden Primary Examine-r Roben F. Stab] [22] Filed: July 31, 1972' Attorney, Agent, or FirmHane, Baxley & Spiecens [21] Appl. No; 276,901

Related US. Application Data 57] ABSTRACT [63] Continuation-impart of Ser. No. 93,995, Dec. 1,

1970 abandoned An illuminating body which is attachable to a parachute is divided into a number of partial flares which g 2 slant outward from the axis of the body at given angles by virtue of the fact that an elongated body of pyro [58] Flew of Search 102/35'4 'g Z 5 technic material is divided into a number of axial sections which fan out from a common connection at one [56] References Cited UNITED STATES PATENTS 4 Claims, 7 Drawing Figures 1,095,869 5/1914 Hyra 102/352 PATENTED FEB I 21974 SHEET 1 [IF 3 l DEVISIBLE PYROTECHNIC DEVICE This application is a continuation-in-part application based on my copending application Ser. No. 93,995 filed Dec. 1, 1970, now abandoned.

This invention relates to a device for causing an improved light emission for a pyrotechnic illuminating or flare body which is provided with a flare dividing mean that divides the body into a number of partial flares. The partial flares, in relation to the lengthwise axis of the body, slant outwardly at predetermined angles and have a shape which allows the formation of spaces between the partial flares. The flare body also is arranged to develop a gas velocity (determinable with the burn velocity of the flare body and the contracting of the partial flares) which contributes to a deflection of the partial flares when a wind blows towards such flares.

The improvement of the light emission occurs not only because the illuminating body gives an increase of the specific intensity of light for larger body diameters 60 mm), but also because the light emanating from the body becomes stable and regular within the sphere of interest, which mostly is a cone shaped from the body outgoing beam sphere with about a 90 angle at the body and suitably symmetrically arranged about a vertical line. The sphere may also be defined by the lighted area on the ground where the intensity of light has a certain number of lux. The intensity of light of the flare body is measured in candela and can be varied with the burn rate and the diameter of the flare.

The specific intensity of light is measured in candela /cm of burn area, while the light yield (the light economy) is measured in candela, sec/gram. The stability of the light depends on the flickering of the partial flares and of the smoke in front of the light-producing frontal areas.

This invention is useful not only with illuminating or flare bodies such as those associated with a shell, rocket or other projectile, or those dropped by bombs, but also with stationary pyrotechnic flare bodies.

in a flare body for use with projectiles, for example, the flare is placed in the projectile so that it will be separated from the projectile a predetermined time after the firing of the projectile and will be ignited at a selected time of separation or immediately thereafter. Moreover, the flare in the mentioned case is provided with delay devices such as a parachute for decreasing the drop speed and brake flaps for reducing rotation about the longitudinal axis. The drop speed of the flare is lowered by the parachute so that the flare can light up a certain area on the ground for a prolongd time.

The most conventional way to arrange the flare up to now is to construct it as a cylinder, locate it substantially vertically in the parachute and ignite the end pointing towards the ground.

The light, in the area on the ground, obtained from the body end becomes unstable due to the appearance of smoke disturbances and marked flickering of the flare. Under favorable circumstances an improvement can be obtained because of a normally occurring substantially conical swinging of the flare body and its parachute. During the swinging, the flare body is slanted so that its longitudinal axis in relation to the vertical line defines an angle which is normally between and 40. A relative wind or draft towards the flare, as caused by the fall of the body towards the ground, can cause a deflection of the flare so as to produce a light-producing frontal area. The relative wind can sweep along this area and drive away smoke and particles produced by the burning of the flare. The light on the respective ground area is, therefore, brighter than before, but the swinging of the flare and parachute causes the light within the ground area to be continuously shifted (become irregular) because the lightproducing frontal area, due to the swinging, continuously shifts its position with respect to the ground and to a certain extent its shape. The irregularity causes the lighted parts of the ground area to change with respect to each other and therefore causes moving shadows which make difiicult the observations of a subject within the ground area. These inconveniences cannot be eliminated by increased light intensity because the shadows then will become deeper.

In addition to these irregularities and instabilities the already known flare body with its parachute also has the disadvantage that it is not possible to increase the intensity of light on the ground area in a technically econonomic way by increasing the diameter of the flare. Practical tests have shown that the specific intensity of light (candela/cm of burning area) is probably most favorable when the flare diameters are 60-70 mm, while for larger diameters the specific intensity of light becomes lower. Therefore, an increase of the flare diameter does not yield an equivalent increase in the intensity of light. As an example of unfavorable specific intensity of light for increasing diameter may be mentioned th atanincrease of the diameter of gives an increase of the area of 180 percent, but an increase of the light intensity of only percent. Thus, even if the total light intensity increases for the larger diameter,

the specific intensity of light of the flare body only reaches 65 percent of that of a flare with the smaller diameter.

This phenonemon can probably be explained by the fact that the light-producing frontal area of the flare in the significant sphere direction cannot be increased very much with increased diameter and by the fact that the particles in the flare prevent the light from other parts of the flare from reaching the ground area.

The present invention solves this problem and the improved light obtained by the invention is obtained by a careful combination of a number of parameters which occur when the flare body is burning. The most important parameters are the angles of the partial flares, the shape of the partial flares and therefore to a certain extent the number of the partial flares and, finally, the gas velocity of the partial flares which depends on the burning velocity of the flare body and on the contracting of the partial flares.

The relative wind is determined by the drop speed of the flare body and its parachute when the flare is lifted by means of a projectile, or dropped by means of a bomb. This drop speed is primarily controlled by the parachute. The relative wind causes the partial flares to be deflected so that each partial flare will show a lightproducing frontal area which points at the significant ground area lit up by the flare body.

The shapes of the partial flares must be so designed that spaces are formed between adjacent partial flares. Each partial flare will also have a relatively large discharge area in which an uncontracted partial flare substantially corresponds to the percentage share of the total burning area of the flare body, i.e., if the number of partial flares is five, each partial flare will display an area which is about percent of the total burning area of the body. The use of spaces apparently indicates that a smaller number of partial flares is more advantageous than a larger number of partial flares because there is a risk that the partial flares will blend together when the number of partial flares is large. Three, four or five is apparently the most advantageous number. The gas velocity that is developed at the flare body has, together with the relative wind, an influence on the deflection of the partial flares. The higher gas velocity, the higher relative wind and/or smaller partial flares are required.

Improved lighting is obtained when the angles of the partial flares and the shape of such flares are combined with the developed gas velocity and the relative wind so that the partial flares cooperate in a flare system where they, together with the relative wind, form an extremely stable flow pattern in which the relative wind sweeps across the light-producing frontal areas of the partial flares and carries from these areas during the burning of the flare body smoke and particles via the spaces between the partial flares during simultaneous comparatively small cooling of the partial flares. The relative wind which encounters the partial flares from below, has a stabilizing influence upon the partial flares such that they have a stable direction without flickering. The relative wind counteracts swinging of the flare body and its parachute, which results in an extremely regular light within the ground area. These facts assure that the light-producing frontal areas of the partial flares are stable in the space and movably only in the vertical line. Certainly a sideward movement of the whole flare body will occur as the body and the parachute will follow the movement of the air, but this lateral movement does not have any influence on the stabilization and the regularity of the light.

The stable flow pattern of the flare system is very sensitive to changes in the mutual relations of the parameters. For example, too large angles of the partial flares may cause the cooling of the partial flares to become too strong and therefore the light yield is lowered. If, instead, the angles are too small the spaces between the partial flares do not occur. Also, the deflection of the partial flares becomes too small in this case, which results in irregular light within the significant ground area due to that considerable smoke formation that cannot be removed, occurs at the partial flares and because of the fact that the partial flares flicker and point their ends at the significant ground areas.

It is a general object of the invention to provide a divisible pyrotechnic device which has the abovedescribed improved lighting properties.-

Briefly, the invention contemplates an illuminating device comprising an elongated body of pyrotechnic material divided into a plurality of sectors which when ignited produces at least one flare at an end thereof and flare dividing means for dividing said flare into a plurality of partial flares in such a way that each partial flare has an initial axis which defines a first given angle with respect to the longitudinal axis of said elongated body and each partial flare is separated from the adjacent partial flare by a second given angle large enough to provide air spaces between adjacent partial flares, said flare dividing means including means for splitting said flare body into said sectors and supporting said sectors at common ends slantwise with respect to said longitudinal axis.

Other objects, features and advantages of the invention will be apparent from the following detailed description when read with the accompanying drawing wherein:

FIG. 1 is a side elevation of a prior art flare body and its parachute;

FIG. 2 is a perspective view of the flare body and parachute according to the invention;

FIG. 3 is an end view of the flare body according to FIG. 2, and in the condition in which it can be packed in a projectile;

FIG. 4 is a sectional view of the flare body, before opening, taken along the line 44 of FIG. 3;

FIG. 5 is the same view of the flare body of FIG. 4 after opening;

FIG. 6 is a diagram showing the significances of the invention in relation to prior art constructions; and

FIG. 7 is a diagram displaying an example of the light at a certain point within the ground area of both the prior art flare body and for a flare body according to the present invention.

In FIG. 1 a prior art illuminating body 1 (a body of pyrotechnic material) is arranged with a parachute 2. The parachute and the flare body 1 are assumed to float towards the ground whereby the ignited flare body 3 is illuminating a selected ground area. The flare body slants because of a mainly conical swinging so that its length axis 4 defines an angle a in relation to a vertical line 5. In this way, the flare 3 will be deflected during the fall of the body by a relative wind A. For a relative wind which corresponds to a fall velocity of the flare body of 2-10 m/s it has been shown that the median value of the angle a is about 15. Thus, the flare 3 has been able to present a light-producing frontal area 3a pointing (within the lines 6 and 7) at the selected ground area because the frontal area has not been disturbed by the smoke 3b generated by the burning of the flare body, the smoke being forced backwards and upwards by the relative wind or draft.

FIG. 2 shows an embodiment where a flare dividing means, hereinafter described, divides the flare produced by the flare body into four partial flares. The flare dividing device includes an outwardly resilient component which cooperates with the flare body. The body is split in its length direction (along its lengthwise axis) into four identical sector-shaped parts 8-11. These four parts are firmly brought together at their ends la which are nearest the parachute. The four parts are even pressed together when the body is placed in the projectile. The resilient component operates on the parts 8-11 when the flare body is expelled from the projectile to cause the parts to take such positions that they slant symmetrically outwards from the ends 1a in relation to the longitudinal axis and define an angle ,8 therewith.

In FIG. 3 the parts 8-11 are pressed together so that they can be placed in the projectile.

The actual configuration of the flare body will now be described with respect to FIGS. 4 and 5. It is assumed that the flare body is separated from the projectile and that it has slowed down both in rotation and forward velocity.

The parachute 2 of FIG. 2 is attached to the body by a strap 12 wrapped about a shaft 13 affixed to a base plate 14. The body is in a canister 15 which can be ejected by means of an explosive charge 16. The charge is fired by a time-delay fuze 17 which is triggered the direction 'of'the relative wind was'i'n'allcases 1 5 i.e. a in the two first cases and B in the third case were is provided with a yieldable flange 15a which clasps the base plate 14. At the separation of the canister, the flange yields and the hot gasses generated by the explosion of the charge 16 will pass through'channels l9 and ignite the first end surfaces of the sectors 8, 9, l0 and 11 of a pyrotechnic composition. Base plate 14 has a central cavity which functions as abearing hole for a spring 21. The spring 21 is attached to base plate 14 and presses against the second end surface walls of the sectors. For each sector, spring 21 presses against those parts of the second end surface walls which are closest to the longitudinal axis of the body and hinges 23 are attached to the outer parts of such surface walls.

'rie'sss 513.614 is previded wimtiamih "'suraes' 14a adjacent each hinge 23. When the charge 16 is fired, the canister 15 will be separated; then the spring a covering 26. The covering 26 permits the burning of the sectors only from the first end surface thereof. The channel 19 passes through a disc which covers the first end surface, the disc being burned or ejected upon ignition of such end surfaces of the sectors. V

The diagram of FIG. 6 shows with the curve 23 how the specific intensity of light I/cm burning area in the selected direction for prior art flare bodies with an undivided flare decreases with increasing diameters of the body, while the curve shows how the specific light intensity in the selected direction increases with increasing diameters for flare bodies which are arranged in accordance with the invention. Curves 29a and 30a illustrate a comparing relation the light intensity I.

The diagrams in F ld iillustrate the variation in tinie of the light intensity at the same point in the ground area lighted by the flare body. Curve 37 refers to an already known flare body with undivided flare substantially pointed at the ground area in accordance with FIG. 1, while curve 32 relates to a flare body using the invention and which divides the flare into partial flares.

Practical tests have 'beenmade in a wind tunnel with 66 mm flare bodies. At first, a flare body was tested separately, thereafter four bodies arranged together in parallel to form a common flare, and finally four flare bodies, which were assembled in accordance with parts of the body in FIG. 2, were tested. The relative wind or draft was corresponding to a fall velocity of 6 m/s and 15 The intensity at a certain point in the selected direction was in the first case 0.6 Med (million candela), while in the second case with four parallel bodies it was as small as 1.4 Mcd. A light intensity was noted in the third case, i.e., the case which corresponds to the invention, which was no less than 3.0 Mcd, i.e., more than four times than the case With only flare body. The third case gave also a much better light distribution (regularity) within the selected ground area. While the light intensity varied very much at different points within the selected area in the first and second test cases, the intensity was nearly uniform at the respective points in the thir gas-r r. t

What is claimed is:

1. An illuminating device comprising an elongated body of a pyrotechnic material longitudinally divided into a plurality of sectors which when ignited produce at least one flare at an end thereof, and flare dividing means for dividing said flare into a plurality of partial flares'in such a way that each partial flare has an initial axis which defines a first given angle with respect to the longitudinal axis of said elongated body and each partial flare is separated from the adjacent partial flare by a second angle large enough to'provide air spaces between adjacent partial flares, said flare dividing means including means for splitting said body into said sectors and supporting said sectors at common ends slantwise with respect to said longitudinal axis, covering means for each of said sectors, one end of each of said covering means including means for igniting the material adjacent to one end and an end wall at the other end, a

common base plate adjacent said end walls, hinge means hinging each of said end walls to said base plate whereby said sectors are outwardly pivotal relative to a longitudinal axis of said body, and spring means outwardly biasing said sectors.

2. The illuminating device of claim 1 wherein a canister supports said body of a pyrotechnic material as a unit, said canister being ejectible from said body. I

3. The illuminating device of claim 1 wherein said spring means includes a helical spring supported by said base plate and pressing against said end walls for causing the same to pivot outwardly.

4. The illuminating device of claim 1, further comprising removable canister housingsaid body of pyrotechnic material, explosive ejecting means for removing said canister from said body, and detonating means for igniting said explosive means. 

1. An illuminating device comprising an elongated body of a pyrotechnic material longitudinally divided into a plurality of sectors which when ignited produce at least one flare at an end thereof, and flare dividing means for dividing said flare into a plurality of partial flares in such a way that each partial flare has an initial axis which defines a first given angle with respect to the longitudinal axis of said elongated body and each partial flare is separated from the adjacent partial flare by a second angle large enough to provide air spaces between adjacent partial flares, said flare dividing means including means for splitting said body into said sectors and supporting said sectors at common ends slantwise with respect to said longitudinal axis, covering means for each of said sectors, one end of each of said covering means including means for igniting the material adjacent to one end and an end wall at the other end, a common base plate adjacent said end walls, hinge means hinging each of said end walls to said base plate whereby said sectors are outwardly pivotal relative to a longitudinal axis of said body, and spring means outwardly biasing said sectors.
 2. The illuminating device of claim 1 wherein a canister supports said body of a pyrotechnic material As a unit, said canister being ejectible from said body.
 3. The illuminating device of claim 1 wherein said spring means includes a helical spring supported by said base plate and pressing against said end walls for causing the same to pivot outwardly.
 4. The illuminating device of claim 1, further comprising removable canister housing said body of pyrotechnic material, explosive ejecting means for removing said canister from said body, and detonating means for igniting said explosive means. 